From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:46346 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751725AbeDVN6o (ORCPT ); Sun, 22 Apr 2018 09:58:44 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, syzbot+1236ce66f79263e8a862@syzkaller.appspotmail.com, Theodore Tso Subject: [PATCH 4.16 099/196] ext4: force revalidation of directory pointer after seekdir(2) Date: Sun, 22 Apr 2018 15:51:59 +0200 Message-Id: <20180422135109.375117801@linuxfoundation.org> In-Reply-To: <20180422135104.278511750@linuxfoundation.org> References: <20180422135104.278511750@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.16-stable review patch. If anyone has any objections, please let me know. ------------------ From: Theodore Ts'o commit e40ff213898502d299351cc2fe1e350cd186f0d3 upstream. A malicious user could force the directory pointer to be in an invalid spot by using seekdir(2). Use the mechanism we already have to notice if the directory has changed since the last time we called ext4_readdir() to force a revalidation of the pointer. Reported-by: syzbot+1236ce66f79263e8a862@syzkaller.appspotmail.com Signed-off-by: Theodore Ts'o Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman --- fs/ext4/dir.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) --- a/fs/ext4/dir.c +++ b/fs/ext4/dir.c @@ -365,13 +365,15 @@ static loff_t ext4_dir_llseek(struct fil { struct inode *inode = file->f_mapping->host; int dx_dir = is_dx_dir(inode); - loff_t htree_max = ext4_get_htree_eof(file); + loff_t ret, htree_max = ext4_get_htree_eof(file); if (likely(dx_dir)) - return generic_file_llseek_size(file, offset, whence, + ret = generic_file_llseek_size(file, offset, whence, htree_max, htree_max); else - return ext4_llseek(file, offset, whence); + ret = ext4_llseek(file, offset, whence); + file->f_version = inode_peek_iversion(inode) - 1; + return ret; } /*